1. Field of the Invention
This invention relates to a gas filter assembly, and more particularly concerns a free-flow gas filter assembly that uses a filter element to filter dirt and water from a gas.
2. Description of the Prior Art
Gas cools as it travels through piping, causing moisture in the gas to form condensation in the pipes. The condensation must be removed in order for pneumatic equipment to operate properly.
The removal of the condensation from the piping is particularly critical in today's sophisticated pneumatic equipment. For example, pneumatic equipment in dental offices and in computer installations requires that no moisture be allowed in the pneumatic gas line.
Conventional gas filter assemblies have baffles and spinners that separate water and dirt from gas by creating a whirling motion in the filter assembly that throws the gas against an inside wall. The moisture in the gas condenses on the walls, falls to the bottom of the assembly, and is drained away.
Other gas filter assemblies filter gas by positioning barriers in the path of the gas so that the moisture in the gas coalesces on the barriers and drops into the bottom of the filter assembly where it is drained.
Other means of condensing the moisture in a gas in a filter assembly may be used, such as passing the gas through wire, fiber pads, or other spirally-wound fiber materials. The devices may be single stage or double stage.
A problem with conventional filter assemblies is that while they separate dirt and water from the gas, the drain often malfunctions and does not allow water to drain from the filter assembly. Consequently, water fills the filter assembly and passes through it to the downstream piping.
Still another means for condensing the moisture in the gas is to pass the gas through a porous filter element. The gas passes through the filter element, but the moisture in the gas does not pass through and instead forms droplets on the outside surface of the filter element that drop into the bottom of the gas filter assembly and are drained from the assembly. The filter element may be made of polyethylene.
Disadvantageously, polyethylene does not prevent the passage of water therethrough if the drain in the filter assembly fails, and the water rises in the bottom of the filter assembly and covers the polyethylene filter element. The pressure of the gas entering the filter assembly forces water through the polyethylene filter element and into the downstream piping.